The present invention relates to an improved connection between an anchor or fastening element and a substrate, such as masonry, cement or stone, using an adhesive or mortar compound to make the connection, and more particularly, provides an improved apertured or porous sleeve-shaped member for use with the anchor and the adhesive.
It has been found that using an apertured sleeve with an adhesively set anchor (sometimes called a composite anchor) in a bore can improve the connection between the anchor and the substrate in certain situations. Apertured sleeves are useful when the anchor is set in the side face of a wall or upwardly into the bottom face of a ceiling. Typically, the anchor used with an apertured sleeve is a threaded steel rod, although any post of any material can be used. Other anchors that may be used include rebar and tubular steel.
When using an adhesive or mortar to set an anchor in a bore, it is important that the anchor be completely surrounded by the adhesive or mortar and that the adhesive or mortar completely fill the space between the anchor and the wall of the bore, such that there are no air pockets. This creates a strong bond between the anchor and the substrate and protects the anchor from corrosion. This condition is generally easily achieved without the use of an apertured sleeve, when the bore is made in a foundation or floor and the adhesive is inserted into the bore from above. The adhesive flows easily to the bottom of the bore, and when the bottom of the bore is reached, it starts to fill the bore, spreading circumferentially to the wall of the bore, generally a cylinder. However, injecting adhesive so as to sufficiently fill a bore when the bore is disposed horizontally, as in a wall, or upwardly, as in a ceiling, can be very difficult.
Apertured sleeves assist with the placement of the adhesive in these situations in a number of ways. They help measure how much adhesive needs to be used with an anchor of selected dimensions, and they help the adhesive to reach the upper surfaces of the bore, and keep the adhesive relatively close to the anchor.
Measurement of the adhesive is achieved by first selecting the length of the sleeve so that it is only slightly longer than that part of the anchor that will be embedded in the substrate. Second, measurement is achieved by closing the end of the sleeve that is inserted into the bore, although it may have apertures like the rest of the sleeve. Generally, the apertured cylindrical sleeve also has a diameter smaller than that of the bore, and larger than that of the anchor. Generally, the sleeve is small enough to slip easily into the bore and large enough to slip easily over the anchor. The apertures in the sleeve are dimensioned to work with particular adhesives. The apertures need to allow uncured adhesive to flow through them when forced under pressure, as when an anchor is inserted into a sleeve filled with adhesive, but also need to slow the flow of adhesive that is merely being inserted in the sleeve during a filling operation. The apertures also need to be spaced sufficiently close so that the adhesive will substantially cover the sleeve where it can escape from the sleeve through the apertures.
With a sleeve formed in this fashion, it is a simple matter to fill or charge the sleeve with adhesives outside of the bore, and then insert the sleeve into the bore. In this manner, an appropriate amount of adhesive is delivered into the bore for a particular anchor. Because the inserted end of the sleeve is closed or partially blocked, the adhesive does not easily flow further into the bore, and if an anchor is inserted quickly into the sleeve and the bore, there will be little opportunity for the adhesive to flow back out of the front opening of the bore. Thus a selected amount of adhesive is collected and situated in the bore and prevented from flowing away from the anchor, and thus will uniformly spread and surround the anchor, filling the clearance or space between the wall of the bore and the outer surface of the anchor, creating a strong connection between the substrate and the anchor along its entire length.
Apertured sleeves are also especially useful when the anchor is set in a hollow substrate or a substrate with an internal open space or spaces such as concrete block or concrete masonry units (CMU). The screen-type sleeve serves to keep the hardenable mass close to the anchor.
Concrete blocks are generally cement and/or concrete formed into rectangular cells. Concrete blocks and concrete masonry units are hollow rather than solid rectangular blocks. A typical concrete block or CMU is generally a rectangular block with 4 full sides or shells surrounding a cavity that opens outwardly through the top and bottom surfaces. Wider concrete blocks and concrete masonry units may be formed with a web that divides the cavity and spans the distance from one side of the block to the other. The walls of the concrete block or CMU can be narrow or thicken depending on the strength needed for the block.
Setting an anchor in a substrate having interior voids such as a concrete block wall or in a masonry wall having an air space between a facade of bricks and the concrete supporting wall creates further difficulties for the insertion of adhesives. Not only can the adhesive flow too far into the bore away from the anchor, and drip down from the upper surfaces of the bore, but it can literally fall into the void completely away from the anchor.
Since it is likely that void in the wall or the cavity in the concrete block is too large for there to be any bonding of the anchor to the substrate by means of the adhesive along substantial portions of its length, the attachment of the portions of the anchor situated in the bore in the wall or shell of the concrete block or the lines of masonry units becomes very crucial. As mentioned above, the apertured sleeve helps distribute the adhesive uniformly around the anchor making sure that as much contact with the masonry substrate is achieved as is possible. Also the apertured sleeve helps protect the anchor from the elements by keeping it surrounded with adhesive, even in portions of the substrate where there is a large cavity and no bond can be created between the substrate and the anchor.
Setting an anchor in a substrate with a void or hollow interior area also creates additional difficulties for creating a strong connection that the current invention seeks to address. With substrates that have voids, it is especially important that a strong bond be made between the substrate and the anchor where that bond is possible. One way of increasing the chance that enough adhesive will fill the space between the anchor and the substrate is to direct the adhesive through various areas of the sleeve along its axial length where the substrate is expected to be by increasing the aperature size or the porosity of the sleeve in those areas with respect to the aperture size in other areas. Thus in the areas with larger aperture size the adhesive will more easily flow through the sleeve and is more likely to reach the substrate.
According to U.S. Pat. No. 4,790,114, granted to Gene Falco, when an anchor exerts ram pressure on an adhesive within a sleeve with a uniform porosity over their axial length more adhesive is pushed radially outward from the sleeve at the distal or insertion end than is extruded from the insertion or proximal end, resulting in a conically tapering displacement of adhesive with the base of the cone being at the distal or insertion end. See U.S. Pat. No. 4,790,114 at column 1, line 34 through 57. According to Falco, “the [adhesive] material moves freely and uniformly toward the leading edge rather than in a significantly radially [sp] direction through the sleeve.”
To combat this problem, Falco in U.S. Pat. No. 4,790,114 teaches a sleeve with an axial section at the trailing end of the screen with a mesh size that is larger than the mesh size of an axial section at the leading end of the screen. The larger mesh size at the trailing end means less resistance to radial extrusion of the adhesive, and, thus, less ram pressure is needed to push adhesive radially outward through the screen, so that enough adhesive will exit the screen at the trailing section and is thus likely to reach the peripheral wall of the bore and bond with the anchor with the substrate, creating a stronger connection.
Falco in U.S. Pat. No. 4,790,114 achieves a screen with two different mesh sizes by bonding two different tubes of two different mesh sizes with a lapping seam and welding, braising or otherwise joining them together.
This is a labor intensive operation that does not lend itself well to automation and insuring quality control through a run of parts. There exists a need in the art to create a sleeve with axial sections having different resitances to radial extrusion of the adhesive that is cost effective to produce and can insure unform quality among parts.
The object of the present invention is to provide a composite anchor capable of being mass produced at a reasonable price, as well as a composite anchor which is easy to handle and has a high resistance to extraction.